class Solution {
    public int uniquePathsWithObstacles(int[][] obstacleGrid) {
        int m = obstacleGrid.length;
        int n = obstacleGrid[0].length;
        // 状态表示 - 机器人到这个方格路径的数量
        int[][] dp = new int[m + 1][n + 1];
        // 初始化
        dp[0][1] = 1;
        for(int i = 1; i <= m; i++){
            for(int j = 1; j <= n; j++){
                // 状态转移方程
                if(obstacleGrid[i - 1][j - 1] == 1){
                    dp[i][j] = 0;
                }else{
                    dp[i][j] = dp[i - 1][j] + dp[i][j - 1];
                }
            }
        }
        return dp[m][n];
    }
}